/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.extensions.sql.impl;



import com.bff.gaia.unified.sdk.extensions.sql.impl.utils.CalciteUtils;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.ImmutableMultimap;

import org.apache.calcite.adapter.enumerable.CallImplementor;

import org.apache.calcite.adapter.enumerable.NullPolicy;

import org.apache.calcite.adapter.enumerable.ReflectiveCallNotNullImplementor;

import org.apache.calcite.adapter.enumerable.RexImpTable;

import org.apache.calcite.linq4j.function.SemiStrict;

import org.apache.calcite.linq4j.function.Strict;

import org.apache.calcite.rel.type.RelDataType;

import org.apache.calcite.rel.type.RelDataTypeFactory;

import org.apache.calcite.schema.Function;

import org.apache.calcite.schema.ImplementableFunction;

import org.apache.calcite.schema.ScalarFunction;

import org.apache.calcite.sql.SqlOperatorBinding;



import java.lang.reflect.Constructor;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;



import static org.apache.calcite.util.Static.RESOURCE;



/**

 * Unified-customized version from {@link org.apache.calcite.schema.impl.ScalarFunctionImpl}, to

 * address BEAM-5921.

 */

public class ScalarFunctionImpl extends UdfImplReflectiveFunctionBase

    implements ScalarFunction, ImplementableFunction {



  private final CallImplementor implementor;



  /** Private constructor. */

  private ScalarFunctionImpl(Method method, CallImplementor implementor) {

    super(method);

    this.implementor = implementor;

  }



  /** Creates {@link org.apache.calcite.schema.Function} for each method in a given class. */

  public static ImmutableMultimap<String, Function> createAll(Class<?> clazz) {

    final ImmutableMultimap.Builder<String, Function> builder = ImmutableMultimap.builder();

    for (Method method : clazz.getMethods()) {

      if (method.getDeclaringClass() == Object.class) {

        continue;

      }

      if (!Modifier.isStatic(method.getModifiers()) && !classHasPublicZeroArgsConstructor(clazz)) {

        continue;

      }

      final Function function = create(method);

      builder.put(method.getName(), function);

    }

    return builder.build();

  }



  /**

   * Creates {@link org.apache.calcite.schema.Function} from given class.

   *

   * <p>If a method of the given name is not found or it does not suit, returns {@code null}.

   *

   * @param clazz class that is used to implement the function

   * @param methodName Method name (typically "eval")

   * @return created {@link ScalarFunction} or null

   */

  public static Function create(Class<?> clazz, String methodName) {

    final Method method = findMethod(clazz, methodName);

    if (method == null) {

      return null;

    }

    return create(method);

  }



  /**

   * Creates {@link org.apache.calcite.schema.Function} from given method. When {@code eval} method

   * does not suit, {@code null} is returned.

   *

   * @param method method that is used to implement the function

   * @return created {@link Function} or null

   */

  public static Function create(Method method) {

    if (!Modifier.isStatic(method.getModifiers())) {

      Class clazz = method.getDeclaringClass();

      if (!classHasPublicZeroArgsConstructor(clazz)) {

        throw RESOURCE.requireDefaultConstructor(clazz.getName()).ex();

      }

    }

    if (method.getExceptionTypes().length != 0) {

      throw new RuntimeException(method.getName() + " must not throw checked exception");

    }



    CallImplementor implementor = createImplementor(method);

    return new ScalarFunctionImpl(method, implementor);

  }



  @Override

  public RelDataType getReturnType(RelDataTypeFactory typeFactory) {

    return CalciteUtils.sqlTypeWithAutoCast(typeFactory, method.getReturnType());

  }



  @Override

  public CallImplementor getImplementor() {

    return implementor;

  }



  private static CallImplementor createImplementor(final Method method) {

    final NullPolicy nullPolicy = getNullPolicy(method);

    return RexImpTable.createImplementor(

        new ReflectiveCallNotNullImplementor(method), nullPolicy, false);

  }



  private static NullPolicy getNullPolicy(Method m) {

    if (m.getAnnotation(Strict.class) != null) {

      return NullPolicy.STRICT;

    } else if (m.getAnnotation(SemiStrict.class) != null) {

      return NullPolicy.SEMI_STRICT;

    } else if (m.getDeclaringClass().getAnnotation(Strict.class) != null) {

      return NullPolicy.STRICT;

    } else if (m.getDeclaringClass().getAnnotation(SemiStrict.class) != null) {

      return NullPolicy.SEMI_STRICT;

    } else {

      return NullPolicy.NONE;

    }

  }



  public RelDataType getReturnType(RelDataTypeFactory typeFactory, SqlOperatorBinding opBinding) {

    // Strict and semi-strict functions can return null even if their Java

    // functions return a primitive type. Because when one of their arguments

    // is null, they won't even be called.

    final RelDataType returnType = getReturnType(typeFactory);

    switch (getNullPolicy(method)) {

      case STRICT:

        for (RelDataType type : opBinding.collectOperandTypes()) {

          if (type.isNullable()) {

            return typeFactory.createTypeWithNullability(returnType, true);

          }

        }

        break;

      case SEMI_STRICT:

        return typeFactory.createTypeWithNullability(returnType, true);

      default:

        break;

    }

    return returnType;

  }



  /**

   * Verifies if given class has public constructor with zero arguments.

   *

   * @param clazz class to verify

   * @return true if given class has public constructor with zero arguments

   */

  static boolean classHasPublicZeroArgsConstructor(Class<?> clazz) {

    for (Constructor<?> constructor : clazz.getConstructors()) {

      if (constructor.getParameterTypes().length == 0

          && Modifier.isPublic(constructor.getModifiers())) {

        return true;

      }

    }

    return false;

  }



  /*

   * Finds a method in a given class by name.

   * @param clazz class to search method in

   * @param name name of the method to find

   * @return the first method with matching name or null when no method found

   */

  static Method findMethod(Class<?> clazz, String name) {

    for (Method method : clazz.getMethods()) {

      if (method.getName().equals(name) && !method.isBridge()) {

        return method;

      }

    }

    return null;

  }

}



// End ScalarFunctionImpl.java